Telephone system



1,654,912 E. L. BAULCH TELEPHONE SYSTEM Filed Deo.1s, 1924 m LQ RECEIVER RECEIVER "6 in Patented Jan. 3, 1928.

UNITEDSTATES PATENT OFFICE.

ERNEST L. BAULCH, OF MILLBRN, JERSEY, AS/SIGNOR TO WESTERN ELECTRIC COMANY, INCOREORATED, OF NEW YORK, N. Y.7 A CORPORATION F NEW YORK.

TELEPHONE sYsTEiut* 1 Appncation inea December 13, 1924. serial 110,755,611.

ivard operators who extend the connections Ordibeyond to the wanted subscribers.

narily, when receiving a. call7 the outward operator selects an idle trunl trom a group ot trunks leading tothe desired exchange and supervises the extension ojt a connection over this trunk by the ain ot a signaling cir- 'cuit common to the group oli' trunks. A socallcd distributor system ot the start-stop vdistributor type is often used in connection with the common signaling circuit :tor the Sending and receiving O supervisory signals .in the Jform ot codes. These code signals are translated into distinctive operations, which in case ot signals sent to the inward operator may cause'the connection of the inward operators telephone to the selected.

trunk and light a signal indicating to the inward operator the particular trunk se# lected or which may result in other supervisory signaling functions required in the setting upof aconnection over trunks of his type.

vThe common signaling circuit may consist oit an ordinary telephone line composited for telegraph use and in which one composite leg is used A*for transmission of superfisory signals in one directionand the other composite leg is used for transmission of supervisory signals in the.opposite direction. A system disclosing thefeatures as voutlined above has been Jr'ullydisclosed in Patent No. 1,578,651, issued to Karl M. Fetzer, March 30, 1926, and it is with an improved signaling circuit for a system of the above type that the present invention is concerned.

An object of the invention is, therefore, to provide a common signaling circuit .for use in connection with straight-forward(trunk ing systems, that is simple in design and inexpensive to installA maintain and 1n which the cost of. the terminal devices pro-v vided in accordance with this invention is insignificant compared with the cost of the standard telegraphequipment `at present employed for rsystems of this type.

*Another object of the/*invention is to pro-,

vide a common signaling circuit that can be easily arranged to t'unctionover -any type of lines, such as composite or simplex lines, suitable for telegraphic transmission.

Another object rot ther-invention is the provision of a common signaling circuit that is less Asensitive to disturbances than ordinary telegraph equipmentsr and thus thoroughly dependable inits operation under the most unfavorable line conditions.

To 4attain these objects vin accordance with onel feature of the` invention there is provided means whereby the transmission ot signals ot' a comparativelyhigh kvoltage or current valu-e maytake place over one coniposite leg ot a pair of telephone lines, vsimplex circuit or overany other line suitable I for the transmission of telegraph signals in one direction and lwhereby the transmission ot' signals of the corresponding values may takeplace in the'opposite direction over' the compositeleg of the same pair of telephone lines, another simplex circuit or over any other line suitable yfor the transmission of telegraph signals. p, l

Another feature of the Vinvention is the provi sion' of terminal apparatus that'transmits'and responds to signals of a comparatively higher current value than are ordinarily'used for telegraphic transmission.

r`Another' feat-ure of the invention is theA provision Aof a Vsimple and inexpensive network for eachchannel to eliminateany disturbing effect that the currents of 'higher values used in this system may have kon adjacent lines. The installation of this additional network. may be done Without disturbing or in anyway changing the existing standard, networks of telephonelines composited or simplexed tortelegraph use.

VThe invention has been illustrated in ther accompanying drawing in connection with a straight-forward Etrunking system employ-- ing'a common signaling circuit and includ# ing theuse oftheso-called start-stop'dis tributors for composing the. variousV signals such as disclosed anddescribed in fthe above mentioned patent. Only a portion of the transmitting distributor at one end and thel receiving distributor at theopposite end for transmission in one direction has been shown in detail, the remainder of the appan Vratus being merely indicated schematically.

merely serves the purpose of illustrating.

how the invention is applied to an existing installation. f

Referring new to the drawing, the portion marked 5 represents the signal coini posing Vequipmentand the portion marked (itl 6. represents the signal translating equipment at one end of the common signaling path 7, While the portions marked 9 and 1() represent the corresponding equipments at the opposite' end of the path 7. Path 7 represents an'ordinary telephone line com posited for. two telegral'ih. channels 11 and l2 vwith telephone equipments 13 and lll and the usual composite line networks 15 and 16 at opposite ends of the line. relay 2Q and network 21 constitute the terminal equip-v ment arranged in accordance with this invention at one end of the path 4' for transmittingsignals over composite leg 11 and relay 22, network 23, keys 2li, 25 and 26 constitute the'terminal equipment arranged in accordance with this invention at the opposite end of Yline 7 for the reception of signals incoming over composite leg 11. The corresponding transmitting and receiving terminal equipments for signals over the other composite leg 12 are correspondingly indicated by boi-:es marked 27 and 28.

rlhe detail operation of the system will now be described in connection with signals transmitted from equipment 5 to equipment 9 over the composite leg 11. 1

It will be noted that relay 2O is normally energized in a eircuit'closed from negative battery, lefthand Winding of relay 20, segment 30, brush 31, segment 32 of'distributor 33 to positive battery. This circuit maintains relay 2O energized in oppositionto current through the right hand winding of the relay,` the circuit for this Winding being normally closed from negative ba'tteryto ground in such a manner as to cause the current in this circuit to oppose the current in the Alower Winding. The purpose of this biasing windingwill be presently described. When now a signal is to be sent the start-stop magnetBa is energized, due to actions taking place inthe equipment indicated by box 46, and releases the arm which thereby is free to rotate over the segments of the distributor 33 for one revolution for each code signal combination and then stopped by the pavvlof magnet 34 which in the meantime has been released. As soon as brush 31 leaves segment 30, the energizing circuit for relay is opened andi-clay 20 is released under the influence of the current through its right hand Winding. The right hand Winding, thereforc, serves as a means to secure a quick release of relay 2O and as Vthe operating characteristics of these two circuits andthe battery supply can kbe readily `struction and inexpensive to manufacture,

will be highly reliable in performance. As the arm proceeds to rotate, the brush 31 closes circuits from the positive battery at segment 32 to segments l0 to l5 in succession and in accordance with the particular code selected causes operations to take place: in the equipment indicated by box 46 that will result in circuits being completed or not, as the case may be, from negative battery, through the left hand `winding of relay 20, to positive battery at 46 which is not shown here but which is provided as indicated in the above mentioned patent.l That is, these functions will take place each time brush 35 passes over thesegments et() to 15. It therefore follows that relay 20'Will be operated` at varying intervals during the passing of brush 35 over lthe segments of distributor 33 to produce a distinctive code signal for cach revolution of the arm 35. operation therefore of relay 20, current from apnegatiife battery Will ybe' supplied at the frontcontact and armature of relay 2O to the compositeleg 11 and upon each` release of relay 20 current from a positivebattery will be applied atthe back Contact land armature of relay V20 to the composite leg 1-1'.

It will be noted that normally the negatire battery at the front contact and Yarmae ture of relay 2O is present on the line 11 to hold relay 22 energized. rlhevcircuit from this battery for relay 22 may be traced as follows: negative battery7 armature and front contact of relay 20, network 15, Windings of coil 21, composite leg 11,'netwerk 16, upper normally closed contactsof reversing key 2l, left handfivinding of relay 22, lower normally closed contacts of key 2K1, toground.

VRelay 22 is also provided with a biasing winding, similar to the right hand biasing Winding of relay 20, throughivhichcurrent Upon each itil).

normally flows ina direction opposite to the normal operating current through the upper Winding of this relay. lilith the circuits afrranged in this manner, relay 22 will be operated and released in synchronism with the operation and release of relay 20, that is, when relay 20 is operated, negative battery through the armature andfront contact will hold relay operated in opposition 'to curs, rent through its right hand Windingand when relay 2O is released, positive battery through the armature and back contact of relay 2O will cause relay 22 torelease with the assurance of the current through Yits lill) utor 33 in a manner Well known in the art.r

for relay 2O is again closed through seg-V ments 32 and 30 by brush 31, and Mcoiise quently relays and 22 are again operated. n L.

lhe operation oi relay 22. causes the circuit forthe start-stop magnetl 5.0 Ato beopened and magnet Consequently released to stop the arm in its normal position.

In order to save battery supply or rather to distribute the Wear on the negatiif'e andpositive batteries equally, the sending ybattery connections are often reversed so that instead of negativer battery being normally connected to the line, positive batterywvill be so connected. lVhen this is done vall thatithe v.attendantl has to do is to operate .the reversing key 24 in order to hold relay 122 normally operated,that fis, the terminals ofv the let't hand Winding of relay 22 are mere-y ly reversed so that the positive current will flow in the same direction through thewinding as did negative current before the key was operated. The keys 25 and 26 are pro-y vided to .cut out the receivingequipment 9 from line 7. f

It these impulses alternately transmitted over leg ll in opposite directions, were of a current value equal to that ordinarily used for metallic telegraph signals they would not be ol suiiicient strength to cause the operation-oli relay 22 or at least not able to operate this relay with any degree of dependability as the least disturbance on the line would interfere with the proper response of this relay. Ordinarily, therefore, in order to secure reliable results Afrom low currentvalues, expensive telegraph equipments had to be employed. lTo eliminate the use of such expensive equipments, the cur'- rent values Were increased and infaccordance With this invention the above inentioned cheap relays substituted. found by actual practice that it was possible It was to dotliis on existing comparatively short compositeI lines when the size of the Wire ywas such as not to introduce a prohibitive iiul'iedauce. .lt was also found that it could be 'done on 4existing' short telephonelines siinplexed for telegraphy Where the size oit the individual wires ot a pair Were'such as not to'peifmit the use of high current values i'oi' eachivirc, but Where the combinedsize of the pair gives satisfactory results. In

this latter case, 2.a different simpleXed lineA must, ot course, be used for the transmission otimpulses in each direction. An varrangement olif-this latter sort may also be .used with advantage Where alarger number of telephone lines are available lthan could possibly be required for telegraph purposes and Yin such cases telephone lilies may often be picked'out in which the s'ze ofthe individual Wires are not suitable for transmission oi signalsr of this increased` current but where the combined size of the line Wires oil' a pair.- permits this to be done. In rsuch instances, thevex'sting nuinber'ot telegraph channels' need not, ot course, be diminished.

Another advantage of this rarrangement is also Athat very little` change needs to be made in the existing standard networks used for duplexiiig or simplexing of `telephone lines. Iii-factfall that has to be done is to add to each line at the sendingend,a simple andV inexpensive retardation ycoil and condenser Wir'es to ground vas shoWnat 2l or at and litl should be noted that tliestand-r.

ard networks need "not be changed or other- `Wisedisturbed inv any manner whatsoever.

The purpose 'of these additional coils and condensers is tofsniooth out the impulses, that (is, secure amore gradual increase vand decrease ofV thelcurrent asit is applied to the line so that no disturbing effects or so-V called thunips will be detected in t-he adjacent Wire of a pair oi' Wires used for this purpose orin other adjacent pairs ot Wires particularly if the lines are grouped in cables.

Perhaps one of the principal advantages, in the long run of this system is itsA simplicity of maintenance over previous systems in which a specially trained telegraph apparatus attendant had to maintain and guard the Morse telegraph equipment, Whereas in this case the attendant of the straight-'fon Ward trunkiiig system involving this common signaling circuit will be ableto maintain and guard the complete system as the functions and general scheme of operation of this coinirioii signaling circuit are iii line with the scheme of operation of the system as a Whole. In this respect, therefore, its

cost ofmaintenance is considerablyreduced.

vWhat is claimed is:

l. In a signaling fsysteiina transmissionv line, a circuit- ,or transmitting impulses inivo tor only of said transmission line and a receiving branch, said transmitting branch being connected between ground and said one conductor of said transmissionline at one end of said transmission line, and said receiving branch being connected between ground and said one conductor of said transmission line at the other end of said transmission line, the impedance of said transmitting branch being greater than thecombined impedancesoi: the remaining elements of said circuit, whereby the fluctuation in potential values along said circuit due to the transmission of impulses is comparatively small along said transmission line.

2. In a signaling system, a low impedance transmission line, a circuit for transmitting impulses including a high impedance transmitting branch, one conductor only of said low impedance transmission line and a low impedance receiving branch, a Vsource of current and a transmitter at said transmitting branch for propagating` impulses, and a devicev for receiving said impulses connected between said receiving branch and ground whereby l'the variation in potential `along said circuit due to the transmission of said impulses is comparatively small along said transmission line. c

3. A' signaling system comprisinga transmitter, a relay actuated thereby, a positive and a negative battery controlled by said relay, a two-conductor transmission line including a transmission network arranged for transmission of current impulses over each conductor independently, the relay being so connected to said transmission lineY that impulses from the said batteries are transmitted over one conductor only, a receiverrresponsive to said impulses atthe opposite end of thevconductor with. whiehthe relay is associated, an impedance connected between the relay and said conductor, :andV

said two conductors in series and directeur`- ai Vrent impulses over one conductor 1n one d1,-

rection and over the other conductor in the opposite direction, positive Vandy negative batteries, a relayconnected to each end of each conductor, one for transmitting and the otherlfor receiving impulses from said batteries, atransmitter at-each end of said line arranged to control a corresponding relayv to alternately transmit positive and negative direct current impulses from said bat teries, the relay at one end transmitting impulses over one conductor and the relay at the opposite end transmitting impulses over the other conductor of said transmission line, a receiver at each end of said transmission line arranged to be controlledby a corresponding relay that receives impulses over the corresponding conductor, and impedance 'means arranged between each transmitting relay and its corresponding conductor, the impedance value oit which and the corre* spending conductor are so proportioned that In witness whereof, I hereunto subscribe my name this 10th day oivDecember, A. D.

1924. p f ERNEST L. BAULOH,l 

